Member having photocatalytic function and method for manufacture thereof

ABSTRACT

A photocatalyst layer (TiO 2 ) is formed on the surface of a substrate (glass plate) through the intermediary of a monoclinic undercoat layer (ZrO 2 ), and no dead layer is substantially present between the photocatalyst layer and the undercoat layer. Also, by providing a peel preventing layer between the substrate and the undercoat layer, it is possible to eliminate film peeling between the photocatalyst layer and the substrate, defects and discoloration. In the above-described TiO 2  layer, metal such as tin (Sn), zinc (Zn), molybdenum (Mo) or iron (Fe) is doped. The phrase “no dead layer is substantially present” means that the thickness of the dead layer is 20 nm or less. The thickness of the photocatalyst layer is preferably from 1 nm to 1,000 nm, more preferably from 1 nm to 500 nm.

TECHNICAL FIELD

The present invention relates to a member with a photocatalyst layerformed on the surface thereof.

BACKGROUND ART

Photocatalysts such as anatase type titanium oxide are known to exertantifouling effect to decompose organic materials under ultravioletlight irradiation, antibacterial activity and hydrophilicity.Additionally, nowadays, photocatalysts exerting a catalytic functionunder visible light irradiation are attracting attention.

Formation of the above-described photocatalyst layer on the surface of amember such as glass is frequently carried out by means of vacuum filmformation methods including sputtering and vapor deposition, orreduced-pressure film-formation methods.

Provision of an undercoat layer between the substrate such as glass andthe photocatalyst layer formed on the surface of the substrate has beenproposed in Japanese Patent Application Publication No. 9-227167,Japanese Patent Application Publication No. 10-66878, Japanese PatentApplication Publication No. 2000-312830, and Japanese Patent ApplicationPublication No. 2001-205094.

Japanese Patent Application Publication No. 9-227167 discloses that abarrier layer is provided between a glass substrate and a photocatalyticcomposition (medium) which is formed on the surface of the substrate forthe purpose of preventing function deterioration of the medium caused byalkali eluted from the glass, and proposes use of zirconium oxide, inparticular, amorphous zirconium oxide as the barrier layer.

Japanese Patent Application Publication No. 10-66878 discloses that aphotocatalyst film is formed on a substrate in a state where anundercoat film is interposed therebetween, and in particular, zirconiumoxide is used as the undercoat film and titanium oxide is used as thephotocatalyst film.

Japanese Patent Application Publication No. 2000-312830 discloses that alayer of a metal oxide such as zirconium oxide is interposed between asubstrate (aluminum) and a photocatalyst layer so as to control oxygendiffusion from the photocatalyst layer to the substrate with the aid ofthe metal oxide layer.

Japanese Patent Application Publication No. 2001-205094 discloseszirconium oxide as a photocatalytic material and discloses that atitanium oxide layer is formed on the exterior of the zirconium oxide.

PCT International Publication (WO 02/40417) discloses that a hightemperature stable type cubic or orthorhombic zirconium oxide layer isformed between a substrate and a titanium oxide layer.

When a photocatalyst layer is formed according to the above-describedmethods, there are cases where no photocatalytic function is exerted, orsuch a function is not exerted unless the thickness of the photocatalystlayer is made thick, which causes the reflectance of the article tobecome large and interference color to be generated, and thereby thecompatibility of the preferable reflectance and color tone with thephotocatalytic activity is hardly achieved. Also, there are drawbacksthat when a high temperature stable type cubic or orthorhombic zirconiumoxide layer needs to be formed, low heat resistance resin and the likecannot be used as a substrate, and photocatalytic members having a largesize for use in construction and the like can be hardly obtained becauseit is technically difficult to heat large size substrates uniformly.

DISCLOSURE OF THE INVENTION

In order to solve the above-described problems, researches were made bythe present inventors, and it turned out that difference in the degreeof crystal growth in a photocatalyst layer causes a state where some ofphotocatalyst layers (TiO₂) exert and others do not exert aphotocatalytic function depending on the film configuration and thefilm-formation conditions even if the photocatalyst layers have the samefilm thickness. More specifically, a photocatalyst layer (TiO₂) in whicha columnar particulate structure of polycrystal or single crystal isformed clearly and continuously from the interface of the substrate tothe surface of the photocatalyst layer exerts a remarkablephotocatalytic effect; however, a photocatalyst layer (TiO₂), in whichno columnar particulate structure is found in the neighborhood of theinterface of the substrate and an amorphous layer (hereinafter referredto as a dead layer) is found instead does not exert any sufficientphotocatalytic effect. Accordingly, the present inventors investigatedmeasures for substantially preventing the above-described dead layerfrom being formed, and discovered that provision of an undercoat layerfor promoting crystal growth in the photocatalyst layer can effectivelycontrol formation of the dead layer.

However, in the case of a configuration in which the above-describeddead layer is substantially absent, since a particulate structure isformed from the undercoat layer to the photocatalyst layer, there arecases where chlorine ions and water pass through the voids in theparticulate structure (columnar structure) and diffuse from the surfacetoward the glass substrate. When such diffusing molecules reach theglass substrate, there are cases where anions such as chlorine ionsreact with alkali ions such as sodium contained in the glass substrateso as to generate salt, which causes film peeling or defects. In orderto prevent such phenomena, provision of a peel preventing layer betweenthe undercoat layer and the substrate has been found to be effective.

The present inventors have achieved the present invention on the basisof the following knowledge:

When a photocatalyst layer is formed through the intermediary of anundercoat layer which promotes the crystal growth of the photocatalyst,the generation of the above-described dead layer can be controlled, andwhen a peel preventing layer is provided between the undercoat layer andthe glass substrate, peeling of the film from the glass substrate andthe generation of defects can be controlled. In addition, an excellentphotocatalytic function can be achieved even if the film formation isconducted at low temperature.

Specifically, according to the present invention, there is provided amember having a photocatalytic function in which a photocatalyst layeris formed on the surface of a substrate through the intermediary of acrystalline undercoat layer, and no dead layer is substantially presentin the neighborhood of the interface between the photocatalyst layer andthe undercoat layer.

According to the present invention, there is also provided a memberhaving a photocatalytic function in which a peel preventing layer whosemain component is an oxide, and oxynitride and a nitride containing atleast one of silicon and tin is provided on the surface of a substrate,a photocatalyst layer is formed on the surface of the peel preventinglayer through the intermediary of a crystalline undercoat layer, and nodead layer is substantially present between the undercoat layer and thephotocatalyst layer. The thickness of the peel preventing layer is 2 nmto 200 nm, preferably 5 nm to 50 nm. When the thickness of the peelpreventing layer is less than 2 nm, the effect of controlling thegeneration of peeling and defects becomes insufficient. On the otherhand, even when the thickness of the peel preventing layer is greaterthan 200 nm, the effect of controlling the generation of peeling anddefects is not largely improved. Therefore, the upper limit of thethickness of the peel preventing layer is preferably 200 nm from theviewpoint of economy. When the thickness of the peel preventing layer isgreater than 5 nm, the water blocking effect more preferably isenhanced. In addition, when the thickness exceeds 50 nm, the stress ofthe amorphous film becomes greater and peeling easily occurs. Therefore,the more preferable upper limit of the thickness of the peel preventinglayer is 50 nm.

An embodiment of the member having a photocatalytic function accordingto the present invention has a configuration in which a photocatalystlayer is formed on the surface of a substrate through the intermediaryof a crystalline undercoat layer, the substrate is a glass substratemanufactured by a float glass method, the undercoat layer is positionedon the tin-containing surface (namely, the tin modification layer or theamorphous tin oxide layer) of the glass substrate, and no dead layer issubstantially present between the undercoat layer and the photocatalystlayer.

Provision of the crystalline undercoat layer can improve thecrystallinity of the photocatalyst layer, and the surface of thephotocatalyst layer can be rapidly made superhydrophilic. Also,provision of the peel preventing layer between the substrate and thecrystalline undercoat layer can control peeling of the undercoat layerfrom the substrate, or defects.

The peel preventing layer whose main component is an oxide, anoxynitride and a nitride containing at least one of silicon and tin hasa capability of blocking a variety of ions and molecules such as achlorine ion and water which penetrate from the outside. Also, when aglass plate manufactured by a float process (for example, a method formanufacturing a glass plate by floating molten glass on molten tin) isused as the substrate, a tin oxide containing layer (tin modificationlayer) is located on the bottom face (which refers to the face incontact with tin; the top face refers to the face not in contact withtin), and this layer functions as the peel preventing layer.

The peel preventing layer blocks chlorine ions and water which penetratefrom the surface, prevents these ions and molecules from reaching theglass substrate, and thereby, it is possible to control peeling of theundercoat layer from the substrate. It is also possible to controldiscoloration or defects caused by reaction of carbonic acid gas andwater from the atmosphere with alkali components in the glass.

The dead layer is a layer in which amorphous (noncrystalline)characteristics are predominant, and the electron diffraction image isobserved as a halo pattern as shown in FIG. 1(a). On the other hand, ina case where a layer is different from a dead layer, diffraction spotsare observed as shown in FIG. 1(b).

The phrase that “no dead layer is substantially present” refers to acase where the thickness of the dead layer is 20 nm or less, or morepreferably 10 nm or less, as well as a case where no dead layer ispresent. The dead layer having such a thickness does not cause so muchdeterioration of the photocatalytic activity which is caused bydeterioration of the crystallinity of the photocatalyst layer.

The thickness of the photocatalyst layer is preferably 1 nm to 1,000 nm.When the thickness is less than 1 nm, the continuity of the film becomespoor and photocatalytic activity becomes insufficient. In contrast, whenthe thickness is greater than 1,000 nm, since exciting light(ultraviolet light) does not reach the deep interior of thephotocatalyst layer, such an increase of the film thickness does notlead to any further improvement of the photocatalytic activity. Inparticular, the effect of the undercoat layer is found to be remarkablein a case where the thickness is in the range from 1 nm to 500 nm. Acomparison made with respect to the same thickness showed that the casewhere the undercoat layer is provided presents a larger photocatalyticactivity than the case where no undercoat layer is provided. Therefore,it can be said that the thickness range of from 1 nm to 500 nm is morepreferable.

Even when the thickness of the photocatalyst layer is made as thin as 1nm to 100 nm, if the particulates constituting the photocatalyst layerare formed continuously from the interface of the undercoat layer to thesurface of the photocatalyst layer, crystal growth is developed, andthereby the photocatalytic activity can be exerted sufficiently.

The width of the particulates constituting the photocatalyst layer alongthe direction parallel to the substrate is preferably 5 nm or more. Thisis because if particulate width is less than 5 nm, the crystallinity islow and the photocatalytic activity becomes insufficient.

Also, in the present invention, it is preferable that the undercoatlayer and the photocatalyst layer are made of a crystalline metal oxideor a crystalline metal oxynitride, and at least one of the distancesbetween oxygen atoms in the crystals which constitute the undercoatlayer is approximate to one of the distances between oxygen atoms in thecrystals which constitute the photocatalyst layer. When thephotocatalyst layer is formed on the undercoat layer, a combination ofthe undercoat layer and the photocatalyst layer which satisfies theabove-described condition allows the photocatalyst layer to grow easilyand quickly as a crystalline one with the aid of the oxygen atoms as thecommon portions.

FIG. 2(a) shows the atomic arrangement in the (111) orientation plane inthe monoclinic zirconium oxide, and FIG. 2(b) shows the atomicarrangement in the (101) orientation plane in the tetragonal (anatasetype) titanium oxide. With respect to the distances between oxygenatoms, the monoclinic zirconium oxide and the tetragonal (anatase type)titanium oxide are similar to each other (in the range of from 90 to110%). Accordingly, if the monoclinic crystalline zirconium compound isused as the undercoat layer, the crystalline film of the tetragonaltitanium oxide can be formed on the undercoat layer easily.

As for the undercoat layer, zirconium oxide to which a small amount ofnitrogen is added, zirconium oxynitride, and zirconium oxide to whichniobium (Nb) of 0.1 to 10 atomic % is added are preferably used as wellas the above-described monoclinic zirconium oxide. When a target towhich niobium is added is used for sputtering, generation of arcing canbe prevented, and undesirable power control and deterioration of thefilm formation rate can be prevented.

As for the photocatalyst layer, the above-described tetragonal titaniumoxide is preferably used. In particular, anatase type titanium oxide ispreferably used because the photocatalytic activity thereof is high. Inaddition to anatase type titanium oxide, rutile type titanium oxide, acomposite oxide of titanium and tin, a mixed oxide of titanium and tin,titanium oxide to which a small amount of nitrogen is added, andtitanium oxynitride are preferably used.

The thickness of the undercoat layer is preferably 1 nm or more and 500nm or less. The thickness of less than 1 nm is not preferable becausethe undercoat layer of such a thickness is not continuous andisland-like, and thereby the durability is decreased. On the other hand,even when the thickness is greater than 500 nm, the effect of thethickness on the photocatalyst layer becomes substantially the same, andincreasing the thickness is economically useless. The more preferablethickness of the undercoat layer is 2 to 50 m-n. When the thickness isless than 2 nm, the crystallinity of the undercoat layer becomes low,and hence the effect of promoting the crystal growth of thephotocatalyst layer becomes small. When the thickness is greater than 50nm, the variation of the optical properties (color tone, reflectance)due to the thickness variation becomes large.

As for the monoclinic zirconium oxide which is preferable for theundercoat layer, the electron diffraction image obtained byperpendicularly irradiating the cross section of the layer of themonoclinic zirconium oxide includes the electron diffraction image fromthe (111) plane or the (−111) plane, and the interplanar spacing withrespect to the (111) orientation plane measured by the above-describedelectron diffraction image or by a bright-field image of a transmissionelectron microscope (TEM) is 2.6 to 3.0 Å, and the interplanar spacingwith respect to the (−111) orientation plane measured by the same methodis 3.0 to 3.5 Å.

In a case where the interplanar spacing of zirconium oxide is not in theabove-described ranges, the zirconium oxide suffers from deformation inthe crystals. Consequently, the film stress becomes great, and peelingeasily occurs. Also, since the oxygen positions in the crystal planesare displaced due to the deformation, the consistency of the oxide suchas titanium oxide or the like constituting the photocatalyst layer withthe oxygen positions becomes low, and thereby no desirable crystalgrowth of the photocatalyst layer is observed.

As for the anatase type titanium oxide which is preferable for thephotocatalyst layer, the electron diffraction image obtained byperpendicularly irradiating the cross section of the layer of theanatase type titanium oxide includes the electron diffraction patternfrom the (101) plane, and the interplanar spacing with respect to the(101) orientation plane measured by the above-described electrondiffraction image or by a bright-field image of a transmission electronmicroscope (TEM) is 3.3 to 3.7 Å.

In a case where the interplanar spacing of titanium oxide is not in theabove-described spacing range, the titanium oxide suffers fromdeformation in the crystals. Consequently, the film stress becomesgreat, and peeling easily occurs. Also, since the oxygen positions inthe crystal planes are displaced due to the deformation, the consistencyof the oxide such as zirconium oxide or the like constituting theundercoat layer with the oxygen positions becomes low, and thereby nodesirable crystal growth of the titanium oxide is observed.

The methods for forming the undercoat layer and the photocatalyst layermay be any of a liquid phase method (a sol-gel method, a liquid phaseprecipitation method, a spray method and a pyrosol method), a vaporphase method (a sputtering method, a vacuum deposition method and a CVDmethod) and the like, and these methods have the effect of improving thecrystallinity of the photocatalyst layer with the aid of the undercoatlayer. However, a vapor phase method such as a sputtering method, adeposition method and the like is more suitable because it is serves togrow crystals, and thereby it shows particularly significant effect inthe present invention.

Additionally, doping of metals in the photocatalyst layer can promotecarrier generation and accordingly enhance the photocatalytic effect.

Examples of the doped metals include Sn, Zn, Mo and Fe, which aresuitably high in the effect of improving the photocatalytic activity.With respect to Sn, Zn and Mo, the addition amount is preferably 0.1mass % or more and 1 mass % or less, more preferably 0.2 mass % or moreand 0.5 mass % or less. With respect to Fe, the content thereof in thephotocatalyst layer is made to be 0.001 mass % to 1.0 mass %. Theselimitations are based on the fact that the effect becomes too small in acase where the addition amount is too small, while too great an amountcauses disorder in the crystal structure of the photocatalyst andgeneration of a recombination center, and thereby the photocatalyticactivity is deteriorated.

Titanium tin composite oxide or titanium tin mixed oxide is used for thephotocatalyst layer. By using titanium oxide containing tin, it ispossible to improve the maintenance of the hydrophilicity withoutdeteriorating the photocatalytic activity of titanium oxide (TiO₂). In acase of forming a film by a sputtering method, the effect of tincontained in the target improves the film formation rate. The content oftin in the photocatalyst layer is 3 atomic % or more and 50 atomic % orless based on the ratio of the number of tin atoms with respect to thetotal number of titanium atoms and tin atoms. When the content of tin isless than 3 atomic %, the effect of the addition of tin is unpreferablysmall. On the other hand, when the content of tin is greater than 50atomic %, the photocatalytic activity is unpreferably deteriorated.

By forming a hydrophilic thin film on the surface of the photocatalystlayer, it is possible to increase the hydrophilic effect. Thehydrophilic thin film is preferably made of at lease one oxide selectedfrom the group consisting of silicon oxide, zirconium oxide, germaniumoxide and aluminum oxide. Among these oxides, silicon oxide ispreferable from the viewpoint of the hydrophilicity improvement effectand durability. It is preferable that the hydrophilic thin film isporous. When the hydrophilic thin film is porous, it is possible toenhance the water holding effect and the maintenance performance of thehydrophilicity. Also, the active species such as active oxygen generatedin the surface of the photocatalyst layer by irradiation of ultravioletlight can reach the surface of an article, so that the photocatalyticactivity of the photocatalyst layer is not so significantly damaged.

As the method for forming a porous hydrophilic thin film, a liquid phasemethod (a sol-gel method, a liquid phase precipitation method, and aspray method) and a vapor phase method (a sputtering method, a vacuumdeposition method and a CVD method) are used. If the generally knownsol-gel method is employed, a porous thin film can be manufacturedeasily; however, when organic polymer and higher alcohol are added intothe raw material solution of the sol gel method, a porous thin film canbe manufactured more easily. As for the vapor phase method such as asputtering method, by adjusting the film formation conditions so as toincrease the dangling bonds in the oxide, for example, by increasing thegas pressure and reducing the oxygen amount in the gas at the time ofsputtering, it becomes possible to manufacture a porous thin film.

The thickness of the hydrophilic thin film is preferably 1 nm or moreand 30 nm or less. If the thickness is smaller than 1 nm, thehydrophilicity is insufficient, while if the thickness is greater than30 nm, the photocatalytic activity of the photocatalyst layer isdamaged. The more preferable range of the thickness is 1 nm or more and20 nm or less. In this range, the maintenance performance of thehydrophilicity is high when it is not irradiated with light.

The method of manufacturing the photocatalytic member according to thepresent invention comprises the steps of forming a peel preventing layerwhose main component is an oxide, an oxynitride and a nitride containingat least one of silicon and tin on the surface of a substrate, forming amonoclinic zirconium oxide layer at low temperature on the peelpreventing layer, and forming a photocatalyst layer constituted of acrystalline phase on the monoclinic zirconium oxide layer. With this, aphotocatalytic member is obtained in which a dead layer observed as ahalo pattern in an electron diffraction image is not substantiallypresent between the monoclinic zirconium oxide layer and thephotocatalyst layer. As the method for forming the monoclinic zirconiumoxide layer, a vapor phase method, in particular, a sputtering method ispreferable.

As described above, according to the present invention, a photocatalystlayer having high photocatalytic activity can be formed, without heatingor at temperature of 150° C. or below, on a substrate or a thin filmhaving low heat resistance, and thereby it becomes possible to combine aphotocatalyst layer with a component having low heat resistance. Also,the present invention can be applied to film formation on a large sizesubstrate such as glass in which uniform heating and control of crackswhich may occur at the time of heating and cooling are difficult.Examples of the above-described substrate having low heat resistanceinclude a resin substrate or a film made of acrylic resin, polyethyleneterephthalate resin, polyurethane resin, polyimide resin and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a transmission electron microscope (TEM) observationpicture showing the electron diffraction pattern in a case where a deadlayer is present; and FIG. 1(b) is a TEM picture showing the electrondiffraction pattern in a case where no dead layer is present.

FIG. 2(a) is a diagram illustrating the atomic arrangement in the (111)plane of monoclinic zirconium oxide, and FIG. 2(b) is a diagramillustrating the atomic arrangement in the (101) plane of anatase typetitanium oxide.

FIG. 3 is a schematic cross-sectional view illustrating a member havinga photocatalytic function according to the present invention.

FIGS. 4(a) to (d) are scanning electron microscope (SEM) observationpictures for Examples 1 and 2 and Comparative Examples 1 and 2,respectively.

FIG. 5 is a graph showing the results of X-ray diffraction measurementsin Example 1 and Comparative Examples 1 and 2 which shows therelationship between the undercoat layer and the crystallinity of TiO₂in the photocatalyst layer.

FIG. 6 is a schematic cross-sectional view illustrating anotherembodiment of a member having a photocatalytic function according to thepresent invention.

FIG. 7 shows optical microscope pictures of the surfaces of Example 18and Comparative Example 16 after a salt spray test which show the effectof the peel preventing layer.

FIG. 8 is a high resolution TEM picture which shows the cross section ofthe ZrO₂ layer and the TiO₂ layer in Example 18.

FIG. 9 is a high resolution TEM picture which shows the cross section ofthe ZrO₂ layer and the TiO₂ layer in Example 17.

FIG. 10 is an X-ray diffraction profile of the sample in Example 17.

BEST MODE FOR CARRYING OUT THE INVENTION

A detailed description will be made below on embodiments of the presentinvention referring to the accompanying drawings. FIG. 3 is a schematiccross-sectional view illustrating a member having a photocatalyticfunction according to the present invention. In this typical example, alayer of crystalline ZrO₂ is formed as an undercoat layer in a thicknessof 56 nm on the surface of a glass plate as a substrate, a layer ofcrystalline TiO₂ in which metal is doped is formed as a photocatalystlayer in a thickness of 140 nm on the ZrO₂ layer, and a porous SiO₂layer is formed in a thickness of 5 nm on the TiO₂ layer so as toenhance the hydrophilicity.

The above-described ZrO₂ layer, TiO₂ layer and SiO₂ layer are formed bya sputtering method. Metal such as tin (Sn), zinc (Zn), molybdenum (Mo)or iron (Fe) is doped at the time of forming the TiO₂ layer.

Table 1 shows the film configuration, the methods for forming the peelpreventing layer, the undercoat layer, the photocatalyst layer and thehydrophilic thin layer, the presence of a dead layer, and the evaluationof the contact angle in Examples 1 to 9. Table 2 shows the filmconfiguration, the methods for forming the peel preventing layer, theundercoat layer, the photocatalyst layer and the hydrophilic thin layer,the presence of a dead layer, and the evaluation of the contact angle inComparative Examples 1 to 11. Table 3 shows the film formationconditions for each film in Table 1 and Table 2 (i.e., the peelpreventing layer, the undercoat layer, the photocatalyst layer and thehydrophilic film). TABLE 1 Film configuration and film formation methodElectron Contact angle evaluation results Peel diffraction UV-θ1 methodpreventing Hydrophilic & TEM Contact angle UV-θ2 method layer UndercoatPhotocatalyst thin layer measurement after UV (UV irradiation,(thickness) layer layer (thickness) Presence/ irradiation stored in Filmformation (thickness) Film (thickness) Film Film formation absence ofOverall dark) Overall Substrate method formation method formation methodmethod dead layer evaluation evaluation Ex. 1 Glass SiO₂ (20 nm)Monoclinic ZrO₂ Anatase TiO₂ Absent 5° (56 nm) (140 nm) SputteringSputtering Sputtering E Ex. 2 Glass SiO₂ (20 nm) Monoclinic ZrO₂ AnataseTi0₂ Absent 4° (56 nm) (140 nm) Sputtering Sputtering Sputtering E Ex. 3Glass Monoclinic ZrO₂ Anatase TiO₂ Present 10° (56 nm) (140 nm) (15 nm)Deposition Deposition G Ex. 4 Glass Monoclinic ZrOxNy Anatase TiOxNyPresent 6° (56 nm) (140 nm) (5 nm) Sputtering Sputtering G Ex. 5 GlassMonoclinic ZrO₂ Anatase TiO₂ Present 7° (56 nm) (140 nm) (10 nm)Deposition Deposition G Ex. 6 Glass Monoclinic ZrO₂ Zn (0.42 wt %)Absent 1° (56 nm) doped TiO₂ (140 nm) Sputtering Sputtering E Ex. 7Glass Monoclinic ZrO₂ Mo (0.35 wt %) Absent 2° (56 nm) doped TiO₂ (140nm) Sputtering Sputtering E Ex. 8 Glass Monoclinic ZrO₂ Fe (0.05 wt %)Absent 2° (56 nm) doped TiO₂ (140 nm) Sputtering Sputtering E Ex. 9Glass Monoclinic ZrO₂ Zn (0.42 wt %) SiO₂ (5 nm) Absent (4°, 10°) (56nm) doped TiO₂ (140 nm) Sputtering Sputtering Sputtering E

TABLE 2 Film configuration and film formation method Electron Contactangle evaluation results Peel Undercoat Photocatalyst Hydrophilicdiffraction UV-θ1 method UV-θ2 preventing layer layer thin layer & TEM(Contact angle method (UV layer (thick- (thickness) (thickness)(thickness) measurement after UV irradiation, ness) Film Film Film FilmPresence/ irradiation) stored in dark) Sub- formation formationformation formation absence of Overall Overall strate method methodmethod method dead layer evaluation evaluation Com. Glass SiO₂ (20 nm)Amorphous Low crystallinity Present 32° (33°, 53°) ex. 1 Si₃N₄ (60 nm)TiO₂ (140 nm) (45 nm thick) Sputtering Sputtering Sputtering B B Com.Glass SiO₂ (20 nm) Low crystallinity Present 35° ex. 2 TiO₂ (140 nm) (50nm thick) Sputtering Sputtering B Com. Glass Amorphous Low crystallinityPresent 29° ex. 3 ZrO₂ (56 nm) TiO₂ (140 nm) (40 nm thick) TransitionSputtering B mode sputtering Com. Glass Amorphous Low crystallinityPresent 38° ex. 4 ZrO₂ (56 nm) TiO₂ (140 nm) (50 nm thick) Ion assistedDeposition B deposition Com. Glass Zn (0.42 wt %) Present 20° ex. 5doped TiO₂ (50 nm thick) (140 nm) Low crystallinity B ↑ Sputtering Com.Glass Zn (1.5 wt %) Present 40° ex. 6 doped TiO₂ (50 nm thick) (140 nm)Low crystallinity B ↑ Sputtering Com. Glass Mo (0.35 wt %) Present 22°ex. 7 doped TiO₂ (50 nm thick) (140 nm) Low crystallinity B ↑ SputteringCom. Glass Mo (1.5 wt %) Present 40° ex. 8 doped TiO₂ (50 nm thick) (140nm) Low crystallinity B ↑ Sputtering Com. Glass Fe (0.05 wt %) Present24° ex. 9 doped TiO₂ (50 nm thick) (140 nm) Low crystallinity B ↑Sputtering Com. Glass Mo (0.1 wt %) Present 37° ex. 10 doped TiO₂ (50 nmthick) (140 nm) Low crystallinity B ↑ Sputtering Com. Glass Lowcrystallinity SiO₂ (5 nm) Present (35°, 38°) ex. 11 TiO₂ (140 nm) (50 nmthick) Low crystallinity Sputtering B ↑ Sputtering

TABLE 3 Film formation conditions (Film formation conditions in Tables 1and 2) ZrO₂ Transition mode Ion assisted ZrOxNy ZrO₂ Si₃N₄ (SiN)Sputtering Sputtering sputtering Deposition deposition SputteringDeposition Sputtering 1) Undercoat layer Target Zr ZrO Zr ZrO Si Gas O₂:100% O₂: 100% O₂: 30%, O₂: 100% O₂: 97%, O₂: 50%, N₂: 100% Ar 70% N₂: 3%Ar: 50% Gas 0.93 Pa 2.0 Pa 0.93 Pa 1.33 × 10⁻²Pa 1.33 × 10⁻²Pa 0.93 Pa1.33 × 10⁻²Pa 0.93 Pa pressure (7 m Torr) (15 m Torr) (7 m Torr) (1 ×10⁻⁴ Torr) (1 × 10⁻⁴ Torr) (7 m Torr) (1 × 10⁻⁴ Torr) (7 m Torr) AppliedRF 2.0 kW RF 2.0 kW DC pulse 3 Å/s 3 Å/s (RF ion RF 2.0 kW 3 Å/s RF 2.0kW power, 100 khz assisted 500 V) etc. 2.0 kW Transfer 58 mm/min 58mm/min 2.9 m/min 8 rpm (rotation) 8 rpm (rotation) 58 mm/min 8 rpm(rotation) 59 mm/min rate Heater None None None None None None None NoneExample 1, 6-9 2 — 5 — 4 3 — Compar- — — 3 — 4 — — 1 ative example 3)Hydrophilic thin film 2) Photocatalyst layer layer (overcoat) or peelTiO₂ (Zn, Mo, preventing layer TiO₂ TiO₂ Fe doped) TiOxNy SiO₂Sputtering Deposition Deposition Sputtering Sputtering Sputtering TargetTi TiO TiO Ti (doped) Ti Si Gas O₂: 100% O₂: 100% O₂: 60%, O₂: 100% O₂:97%, O₂: 50%, Ar: 50% Ar: 40% N₂: 3% Gas 0.93 Pa 1.33 × 10⁻² Pa 1.33 ×10⁻² Pa 0.93 Pa 0.93 Pa 0.40 Pa 0.93 Pa pressure (7 m Torr) (1 × 10⁻⁴Torr) (1 × 10⁻⁴ Torr) (7 m Torr) (7 m Torr) (3 m Torr) (7 m Torr)Applied DC 2.88 kW 3 Å/s 3 Å/s DC 2.88 kW DC 2.88 kW RF 2.0 kW RF 2.0 kWpower, etc. Transfer 1 m/min 8 rpm (rotation) 8 rpm (rotation) 1 m/min 1m/min 1 m/min 0.98 m/min rate Heater None None None None None None NoneExample 1, 2 5 3 6-9 4 1, 2 9 Compar- 1-3, 11 4 — 5-10 1, 2 11 ativeexampleThe number of the film formation pass was appropriately adjusted so asto achieve a predetermined thickness.

In the hydrophilicity evaluation, UV-θ1 method and UV-θ3 method wereadopted in a case where a hydrophilic thin film was not coated, andwhile UV-θ2 method was adopted in a case where a hydrophilic thin filmwas coated. UV-θ1 method is a method in which irradiation withultraviolet black light having an intensity of 1 mW/cm² is conducted for15 minutes, and the contact angle with respect to pure water is measuredimmediately after completion of the irradiation. UV-θ3 method is amethod in which the period of time for the ultraviolet light irradiationin UV-θ1 method is changed to 60 minutes. When the contact angle withrespect to pure water is small, which means that the hydrophilicity ishigh, it can be said that the photocatalytic activity is high, and alsothe antifouling property is high. The overall evaluation was conductedbased on the following reference. UV-θ1 method and UV-θ3 method Contactangle θ after ultraviolet Photocatalytic activity evaluation lightirradiation Excellent (E)     θ ≦ 5° Good (G)   5° < θ < 10° Mean (M)10° ≦ θ < 20° Bad (B) 20° ≦ θ     

UV-θ2 method was basically applied to a case where a hydrophilic thinfilm was coated onto the surface of a photocatalyst layer. In such acase where a hydrophilic thin film is coated, the initial contact angleis small, and thereby a comparison of the contact angles beforeultraviolet light irradiation and after ultraviolet light irradiation isdifficult. Therefore, liquid of 5 ml which constituted of hexane,2-propanol and propionic acid at a ratio of 6:1:3 was applied onto thesurface, and the contact angle change caused by ultraviolet lightirradiation (1 mW/cm², 15 minutes) was measured. The contact angleimmediately after completion of the ultraviolet light irradiation can beconsidered an index of the photocatalytic activity and the antifoulingproperty. Also, the contact angle was measured after storage in the darkfor 2 weeks subsequent to completion of the ultraviolet lightirradiation, and the results ware used as an index of the maintenanceperformance of the hydrophilicity based on the following reference.UV-θ2 Performance evaluation Contact angle θ′ after storing in darkExcellent (E)      θ′ ≦ 15° Good (G) 15° < θ′ ≦ 25° Mean (M) 25° < θ′ <30°  Bad (B) 30° ≦ θ′    

FIGS. 4(a) to (d) are scanning electron microscope (SEM) observationpictures for Examples 1 and 2 and Comparative Examples 1 and 2,respectively. As shown in FIGS. 4(a) and (b), a columnar particulatephotocatalyst layer (TiO₂) is formed on the undercoat layer (crystallineZrO₂) in Examples 1 and 2.

On the other hand, as shown in FIG. 4(c), in Comparative Example 1,although a columnar particulate photocatalyst layer (TiO₂) is formed,the thickness thereof is small, and a dead layer is formed around theinterface between the amorphous undercoat layer (Si₃N₄) and thephotocatalyst layer (TiO₂).

Also, as shown in FIG. 4(d), in Comparative Example 2 where no undercoatlayer is provided, titanium oxide (TiO₂) in the photocatalyst layer doesnot grow into large particles, which suggests that the crystallinity islow.

FIG. 5 is a graph showing the results of thin film X-ray diffractionmeasurements for Example 1 and Comparative Examples 1 and 2. From theresults, it was confirmed that TiO₂ of Example 1 where the undercoatlayer was constituted of crystalline ZrO₂ showed a diffraction peakwhich was ascribable to anatase (101), and the crystallinity of the TiO₂was high. On the other hand, TiO₂ of Comparative Example 1 where theundercoat layer was constituted of amorphous Si₃N₄ showed a crystal peakof rutile (110) to some extent, but did not show a crystal peak ofanatase (101), and in Comparative Example 2 where no undercoat layer wasprovided, neither a crystal peak of anatase (101) nor a crystal peak ofrutile (110) was observed. With this, it was confirmed that thecrystallinity of the TiO₂ in Comparative Examples was low. The TiO₂ ofComparative Examples had low crystallinity or no crystallinity by theX-ray analysis, but it was confirmed that microcrystals of anatase orrutile were present on a dead layer which was observed as a halo patternaccording to an electron diffraction. Such TiO₂ will be hereinafterreferred to as low crystalline TiO₂.

As can be seen from the above-described experimental results, thepresence of the dead layer prevents the particulate crystal structure ofthe photocatalyst layer from growing, which causes low photocatalyticactivity. Specifically, it can be seen that the absence of the deadlayer verifies the growth of the particulate crystal structure of thephotocatalyst layer (TiO₂) which is necessary for exerting highphotocatalytic activity. In order to prevent the dead layer from beinggenerated, it is necessary that at least a crystalline undercoat layeris present under the photocatalyst layer, and it can be said thatformation of an anatase type TiO₂ layer on a monoclinic ZrO₂ undercoatlayer is most suitable for enhancing the crystallinity of TiO₂.

In Comparative Examples 3 and 4, a TiO₂ layer was formed on an amorphousZrO₂ undercoat layer. In Comparative Example 3, the amorphous ZrO₂ layerwas obtained by conducting film formation by transition mode sputtering.In Comparative Example 4, the amorphous ZrO₂ layer was obtained byemploying an ion assisted deposition method so as to eject oxygen ionsinto a film and thereby disorder the structure of the film. The TiO₂layer formed on such an amorphous ZrO₂ undercoat layer has lowcrystallinity, and a thick dead layer was formed in this instance, whichis different from Examples where the TiO₂ layer was formed on themonoclinic ZrO₂ undercoat layer. Consequently, it is not the material ofthe undercoat layer but the crystallinity of the undercoat layer thataffects the crystallinity of the TiO₂ layer.

Now, a brief description will be made below on the transition modesputtering method which was employed for film formation of the zirconiumoxide film in Comparative Example 3 and Comparative Example 13. Inreactive sputtering from a metal target, when oxidation occurs on thesurface of the metal target, the film formation rate comes to belowered. Accordingly, by sensing the oxidation state of the targetthrough monitoring the emission state of oxygen with a plasma emissionmonitor, and by performing feedback of the obtained information to thegas flow rate control system, it becomes possible to form an oxide filmat a higher film formation rate. This method is referred to as atransition mode sputtering method.

Next, a description will be made below on the film formation exampleswith respect to the peel preventing layer formed between the substrateand the undercoat layer, and on the results of a salt spray test. Table4 shows the film configuration, the methods of forming the peelpreventing layer, the undercoat layer, the photocatalyst layer and thehydrophilic thin layer; the presence of a dead layer, the results ofcontact angle evaluation, and the results of a salt spray test inExamples 10 to 17 and Comparative Examples 12 and 13. Table 5 shows thefilm formation conditions for the peel preventing layer, and the filmformation conditions for the other films (the undercoat layer and thephotocatalyst layer). TABLE 4 Contact angle evaluation Filmconfiguration and film formation method Electron results Peel UndercoatPhoto- diffraction UV-θ1 method preventing layer catalyst & TEM Contactangle Salt layer (thick- (thickness) layer (thick- measurement after UVspray ness) Film Film ness) Film Presence/ irradiation test formationformation formation absence Overall Evaluation Substrate method methodmethod of dead layer evaluation results Ex. 10 Glass SiO₂ (20 nm)Monoclinic Anatase Absent 5° G (bottom face) ZrO₂ (56 nm) TiO₂ (140 nm)Sputtering Sputtering Sputtering E Ex. 11 Glass SiO₂ (20 nm) MonoclinicAnatase Absent 4° G (bottom face) ZrO₂ (56 nm) TiO₂ (140 nm) SputteringSputtering Sputtering E (15 m torr) Ex. 12 Glass SiO₂ (20 nm) MonoclinicAnatase Absent 9° G (bottom face) ZrO₂ (56 nm) TiO₂ (50 nm) SputteringSputtering Sputtering G Ex. 13 Glass SiOxNy (20 nm) Monoclinic AnataseAbsent 9° G (bottom face) ZrO₂ (56 nm) TiO₂ (50 nm) SputteringSputtering Sputtering G Ex. 14 Glass SixNy (20 nm) Monoclinic AnataseAbsent 9° G (top face) ZrO₂ (56 nm) TiO₂ (50 nm) Sputtering SputteringSputtering G Ex. 15 Glass SnO₂ (20 nm) Monoclinic Anatase Absent 9° G(top face) ZrO₂ (56 nm) TiO₂ (50 nm) Sputtering Sputtering Sputtering GEx. 16 Glass

Tin modifi- Monoclinic Anatase Absent 9° M (bottom face) cation layerZrO₂ (56 nm) TiO₂ (50 nm) Sputtering Sputtering G Ex. 17 Glass SiO₂ (20nm) Monoclinic Anatase Absent 5° E G (top face) ZrO₂ (56 nm) TiO₂ (150nm) Sputtering Sputtering Sputtering E Com. Glass Low crystallinityPresent 30° B ex. 12 (top face) TiO₂ (50 nm) (ca. 50 nm Baking, 250° C.,thick) B 1 hr after sputtering Com. Glass Amorphous Low crystallinityPresent 31° B ex. 13 (top face) ZrO₂ (56 nm) TiO₂ (50 nm) (ca. 50 nmTransition Baking, 250° C., thick) B mode 1 hr after sputteringsputtering

TABLE 5 Film formation conditions (Film formation conditions for thefilms in Table 4) 1) Peel preventing layer SiO₂ SiOxNy SixNy SnO₂Sputtering Sputtering Sputtering Sputtering Target Si Si Si Sn Gas O₂:50%, Ar: 50% N₂: 50%, O₂: 50% N₂: 100% O₂: 100% Gas pressure 0.93 Pa0.93 Pa 0.93 Pa 0.93 Pa (7 m Torr) (7 m Torr) (7 m Torr) (7 m Torr)Applied power, RF 2.0 kW RF 2.0 kW RF 2.0 kW DC 2.4 kW etc. Transferrate 1 m/min 500 mm/min 177 mm/min 665 mm/min Heater None None None NoneExample 10-12, 17 13 14 15 Comparative — — — — example 2) Undercoatlayer ZrO₂ 3) Photocatalyst layer ZrO₂ ZrO₂ Transition mode TiO₂Sputtering Sputtering sputtering Sputtering Target Zr Zr Zr Ti Gas O₂:100% O₂: 100% O₂: 30%, Ar: 70% O₂: 100% Gas pressure 0.93 Pa 2.0 Pa 0.93Pa 0.93 Pa (7 m Torr) (15 m Torr) (7 m Torr) (7 m Torr) Applied DC pulseDC pulse DC pulse DC: 2.88 kW power, etc. 100 khz 100 khz 100 khz 5.5 kW5.5 kW 2.0 kW Transfer rate 1 m/min 1 m/min 2.9 m/min 1 m/min HeaterNone None None None Example 10, 12-17 11 — 10-17 Comparative — — 13 12,13 exampleThe number of the film formation pass was appropriately adjusted so asto achieve a predetermined thickness.

The salt spray test was conducted as follows:

Sodium chloride (extra pure reagent) was dissolved into ion-exchangewater to prepare about 5% saline water. A test sample of 100×100 mm wasfixed in an apparatus (CASSER-ISO-3, manufactured by Suga TestInstruments Co., Ltd.) so as to incline by 20±5 degrees from thevertical line, and the saline water was sprayed onto the test sample ata rate of 1 to 2 ml/hr. After the continuous spraying for 120 hours, thetest sample was taken out and film peeling was observed.

The durability with respect to saline water was evaluated according tothe following classification:

G (Good) . . . No film peeling and defect can be observed by a visualinspection and with an optical microscope.

M (Mean) . . . Defects can be partly observed with an opticalmicroscope.

B (Bad) . . . Film peeling can be observed by a visual inspection orwith an optical microscope.

According to the test results shown in Table 4, a peel preventing layer(SiO₂, SixNy, SnO₂, and SiOxNy) was formed on the glass substrate, andno film peeling and no defect was observed by a visual inspection andwith an optical microscope in Examples 10 to 15 and 17. In Example 16where the undercoat layer and the photocatalyst layer were formeddirectly on the bottom face of a glass substrate manufactured by a floatprocess, since the tin modification layer present on the bottom faceblocks various kinds of ions and molecules to some extent, no filmpeeling was observed by a visual inspection and with an opticalmicroscope, and defects were only partly observed with an opticalmicroscope. In Comparative Examples 12 and 13 where no peel preventinglayer was provided, film peeling was observed.

Next, a description will be made below on another embodiment of thepresent invention with reference to FIG. 6. A description will beomitted on the same matters as the above-described Examples. FIG. 6 isanother cross-sectional view of a member having a photocatalyticfunction according to present invention, which shows a schematic diagramillustrating the relationship between the columnar particulate structureof the film and the crystallites. In this embodiment, a peel preventinglayer is formed on the surface of a glass plate as a substrate, amonoclinic ZrO₂ layer is formed as an undercoat layer, and a crystallineTiO₂ layer is formed as a photocatalyst layer on the monoclinic ZrO₂layer.

Table 6 shows Examples 18 to 26 and Comparative Examples 14 to 16 withrespect to the relatively thin peel preventing layer, the monoclinicZrO₂ undercoat layer and the photocatalyst layer. TABLE 6 Examples andcomparative examples with respect to the peel preventing layer thin filmand the monoclinic undercoat layer thin film Peel preventingPhotocatalyst Salt layer Undercoat layer layer spray MechanicalSubstrate (thickness) (thickness) (thickness) UV-θ3 test durability Ex.18 Glass (top face) SiO₂ (10 nm) (10 nm) TiO₂ (10 nm) 6° G G Ex. 19Glass (top face) SiO₂ (5 nm) (10 nm) TiO₂ (10 nm) 6° G G Ex. 20 Glass(top face) SiO₂ (2 nm) (10 nm) TiO₂ (10 nm) 8° M G Ex. 21 Glass (topface) SiO₂ (10 nm) Monoclinic ZrO₂ (5 nm) TiO₂ (5 nm) 7° G G Ex. 22Glass (top face) SiO₂ (5 nm) Monoclinic ZrO₂ (5 nm) TiO₂ (5 nm) 7° G GEx. 23 Glass (top face) SiO₂ (10 nm) Monoclinic ZrO₂ (3 nm) TiO₂ (3 nm)10°  G M Ex. 24 Glass (top face) SiO₂ (10 nm) Monoclinic ZrO₂ (5 nm)TiO₂ (10 nm) 7° G G Ex. 25 Glass (top face) SiO₂ (10 nm) Monoclinic ZrO₂(2 nm) TiO₂ (10 nm) 9° G G Ex. 26 Glass (top face) SiO₂ (10 nm) (10 nm)TiO₂ (600 nm) 2° G M Com. ex. 14 Glass (top face) SiO₂ (0.5 nm)Monoclinic ZrO₂ (5 nm) TiO₂ (10 nm) 6° B M Com. ex. 15 Glass (top face)SiO₂ (10 nm) — TiO₂ (10 nm)        52° (No catalytic  G G activity) Com.ex. 16 Glass (top face) — (10 nm) TiO₂ (10 nm) 7° B G(Note)The average temperature of the substrate at the time of each filmformation was about 60° C. (based on thermolabel).Only in Example 26, the average temperature of the substrate at the timeof each film formation was about 120° C. (based on thermolabel).

The mechanical durability test shown in Table 6 was conducted by thefollowing procedure, conditions, evaluation reference:

1) The abrasion resistance test was conducted by using a Taber testingmachine under the conditions that the load was 500 g, the number ofrotation was 10, and the speed of rotation was 60 rpm.

2) Ultrasonic cleaning was conducted for 5 minutes in acetone, andthereafter UV ozone cleaning was conducted for 3 minutes.

3) Observation and evaluation of the sample were made by a visualinspection.

Evaluation Reference

-   -   G (Good): No problem.    -   M (Mean): Abrasive scratches were partly observed.    -   B (Bad): Film peeling partly occurred.

Table 7 shows the film formation conditions for each film (the peelpreventing layer, the undercoat layer, and the photocatalyst layer) ofExamples 18 to 26 shown in Table 6. FIG. 7 also shows the opticalmicroscope pictures of Example 18 (having a peel preventing layer) andComparative Example 16 (having no peel preventing layer) after a saltspray test. No film peeling was observed in Example 18 having a peelpreventing layer, while spot-like film peeling was observed inComparative Example 16 having no peel preventing layer, which verifiesthe effect of the peel preventing layer.

From the above-described results, it was confirmed that the peelpreventing layer, the undercoat layer and the photocatalyst layer areexcellent in the contact angle evaluation results, the salt spray testresults and the mechanical durability even if the peel preventing layer,the undercoat layer and the photocatalyst layer has a small thickness ofaround 5 to 10 nm. When each layer has a small thickness as describedabove, a photocatalytic member in which the reflectance is low, thereflection color tone is neutral and the color tone unevenness is absentcan be obtained, and such a member can be suitably applied particularlyto glass for use in construction. TABLE 7 Experimental conditions forthe examples in Table 6 1) Peel preventing layer SiO₂ Sputtering TargetSi Gas O₂: 50%, Ar: 50% Gas pressure 0.93 Pa (7 m Torr) Electric powersupply, etc. DC Transfer rate 1 m/min Heater None Example 18-26Comparative example 14, 15 2) Undercoat layer ZrO₂ Sputtering Target ZrGas O₂: 100% Gas pressure 0.93 Pa (7 m Torr) Electric power supply, etc.DC pulse Transfer rate 1 m/min Heater None Example 18-26 Comparativeexample 14, 16 3) Photocatalyst layer TiO₂ Sputtering Target Ti Gas O₂:100% Gas pressure 0.93 Pa (7 m Torr) Electric power supply, etc. DCTransfer rate 1 m/min Heater None Example 18-26 Comparative example 14,16The applied power and the number of the film formation pass wereappropriately adjusted so as to achieve a predetermined thickness.

Table 8 shows a comparison of the hydrophilization properties and thefilm formation rate of the titanium tin oxide layer on the monoclinicZrO₂ undercoat layer in Examples 18 and 27 to 29. Table 9 shows the filmformation conditions for the photocatalyst layer of Examples in Table 8,wherein the film formation conditions for the other layers, i.e., thepeel preventing layer and the undercoat layer are the same as thoseshown in Table 7. It can be seen that the use of titanium oxide to whichtin is added improves the hydrophilicity maintenance property in thedark. Also, it can be confirmed that the addition of tin improves thefilm formation rate in a sputtering method.

Table 10 shows the X-ray diffraction results and the TEM observationresults with respect to the sample of Examples 18 and 17. It is apparentfrom Table 10 that the ZrO₂ undercoat layer is monoclinic, and thecrystal structure of the photocatalyst layer TiO₂ is an anatasestructure. TABLE 8 Comparison of the hydrophilization properties and thefilm formation rate of the titanium tin oxide formed on the monoclinicundercoat layer film Peel Hydrophilicity (Ti—Sn film preventingUndercoat Photocatalyst maintenance formation rate)/ layer layer layerproperty in dark (Ti film Substrate (thickness) (thickness) (thickness)UV-θ3 (Note 1) formation rate) Ex. 18 Glass SiO₂ (10 nm) Monoclinic ZrO₂TiO₂ (10 nm) 6° 25° 1.0 (10 nm) Ex. 27 Glass SiO₂ (10 nm) MonoclinicZrO₂ Sn (5 at %) 6° 18° 1.2 (10 nm) doped TiO₂ (10 nm) Ex. 28 Glass SiO₂(10 nm) Monoclinic ZrO₂ Sn (30 at %) 8° 16° 1.9 (10 nm) doped TiO₂ (10nm) Ex. 29 Glass SiO₂ (10 nm) Monoclinic ZrO₂ Sn (45 at %) 10°  15° 3.0(10 nm) doped TiO₂ (10 nm)X-ray diffraction profile measurement shows that these tin dopedphotocatalyst films are excellent in crystallinity and tend to haverutile crystallinity.Note 1)After measurement was made by UV-θ3 procedure, the sample was stored inthe dark for 1 week, and thereafter the contact angle with respect topure water (while being increased) was measured.

TABLE 9 (Experimental conditions for Examples in Table 8) Photocatalystlayer TiO₂ Sputtering Sputtering Sputtering Sputtering Target Ti Ti—SnTi—Sn Ti—Sn (Sn: 5 at %) (Sn: 30 at %) (Sn: 45 at %) Gas O₂: 100% O₂:100% O₂: 100% O₂: 100% Gas pressure 0.93 Pa 0.93 Pa 0.93 Pa 0.93 Pa (7 mTorr) (7 m Torr) (7 m Torr) (7 m Torr) Electric power DC DC DC DCsupply, etc. Transfer rate 1 m/min 1 m/min 1 m/min 1 m/min Heater NoneNone None None Example 18 27 28 29The peel layers and undercoat layers were embodied under the sameconditions as those shown in Table 7.The applied power and the number of the film formation passes wereappropriately adjusted for the purpose of achieving the respectivepredetermined thicknesses.

TABLE 10 Interplanar spacing and Miller indices measured from the TEMbright-field image Interplanar spacing and crystal Interplanar spacingand crystal system of ZrO₂ in JCPDS system of TiO₂ in JCPDS Othercrystal Other crystal Observed systems were systems were Observed deniedfrom an denied from an with a loupe ZrO₂ Monoclinic XD peak. Anatase XDpeak. (a) Glass/SiO₂ (10 nm)/ZrO₂ (10 nm)/TiO₂ (10 nm) (Sample ofExample 18 and FIG. 8) ZrO₂ 2.867  (111) 2.841 3.185 (−111) 3.165 3.358(−111) 3.165 TiO₂ 3.544 (101) 3.520 3.503 (101) 3.520 (b) Glass/SiO₂ (20nm)/ZrO₂ (100 nm)/TiO₂ (150 nm) (Sample of Example 17 and FIG. 9) ZrO₂2.831  (111) 2.841 3.109 (−111) 3.165 3.731 (−111) 3.698 TiO₂ 3.449(101) 3.520The film formation conditions follow Table 7.

In order to verify the above-described results, a high resolution TEMpicture of Example 18 is shown in FIG. 8. FIG. 8 shows a structure inwhich the (−111) plane of ZrO₂ (monoclinic) is continuous with the (101)plane of TiO₂ (anatase) with an inclination is observed in the TiO₂ filmwhich is grown on the ZrO₂ film.

A high resolution TEM picture of the cross section of the ZrO₂ film andthe TiO₂ film in Example 17 is shown in FIG. 9. The ZrO₂ film and theTiO₂ film in Example 17 has a thickness of 10 times or more compared toeach film in Example 18. A lattice pattern is found on the interfacewith respect to each thin film, and this figure shows that a structurein which the monoclinic ZrO₂ (−111) plane is continuous with the anatasetype TiO₂ (101) plane is observed. This figure also shows that themonoclinic ZrO₂ (110) plane is continuous with the anatase type TiO₂(101) plane in some portions. FIG. 10 shows an X-ray diffraction profileof Example 17, in which peaks of the anatase type TiO₂ and themonoclinic ZrO₂ were observed.

INDUSTRIAL APPLICABILITY

As described above, when a photocatalyst layer is formed on the surfaceof a substrate, by providing a crystalline (monoclinic) undercoat layerand forming the photocatalyst layer on the undercoat layer, thephotocatalyst crystals are allowed to grow continuously up to thesurface of the photocatalyst layer. Also, by providing a peel preventinglayer between the substrate and the undercoat layer, peeling and defectscan be controlled. As a result, it is possible to obtain a member havinghigh photocatalytic activity and a high antifouling property which canbe applied to all the members for use in glass panes for construction,glass plates for displays, glass substrates for DNA analysis, portableinformation devices, sanitary equipments, medical care equipments,biomedical test chips, materials for hydrogen/oxygen generation devices,and the like.

Also, by forming the peel preventing layer whose main component is anoxide, an oxynitride and a nitride containing at least one of siliconand tin on the surface of the substrate, forming the monocliniczirconium oxide layer, for example, at low temperature of 150° C. orbelow, and thereafter forming the photocatalyst layer comprising acrystalline phase, it becomes possible to combine with a material havinglow heat resistance. In addition, since precise control of thetemperature distribution in heating is not required, the presentinvention can be applied to film formation on a large size plate glasseasily.

1. A member having a photocatalytic function comprising: a substrate; anundercoat layer provided on said substrate; and a photocatalyst layerformed on said undercoat layer, wherein said undercoat layer iscrystalline, said photocatalyst layer is constituted of a crystallinephase, and no dead layer which is observed as a halo pattern in anelectron diffraction image is substantially present between saidundercoat layer and said photocatalyst layer.
 2. A member having aphotocatalytic function comprising: a substrate; a peel preventinglayer, whose main component is an oxide, an oxynitride or a nitride ofat least one of silicon and tin, provided on the surface of saidsubstrate; an undercoat layer provided on said peel preventing layer;and a photocatalyst layer formed on the surface of said undercoat layer,wherein said undercoat layer is crystalline, said photocatalyst layer isconstituted of a crystalline phase, and no dead layer which is observedas a halo pattern in an electron diffraction image is substantiallypresent between said undercoat layer and said photocatalyst layer. 3.The member having a photocatalytic function according to claim 2,wherein the thickness of said peel preventing layer is from 2 nm to 200nm.
 4. The member having a photocatalytic function according to claim 2,wherein said substrate is a glass plate manufactured by a float process,and said peel preventing layer is a tin modification layer formed on thebottom face of said glass plate at the time of manufacturing said glassplate.
 5. The member having a photocatalytic function according to claim2, wherein the thickness of said dead layer is 0 nm or more and 20 nm orless.
 6. The member having a photocatalytic function according to claim2, wherein the thickness of said photocatalyst layer is from 1 nm to1,000 nm.
 7. The member having a photocatalytic function according toclaim 2, wherein the thickness of said undercoat layer is from 1 nm to500 nm.
 8. The member having a photocatalytic function according toclaim 2, wherein the particulates which constitute said photocatalystlayer are formed continuously from the interface with the undercoatlayer to the surface of the photocatalyst layer.
 9. The member having aphotocatalytic function according to claim 8, wherein the width of theparticulates which constitute said photocatalyst layer along thedirection parallel to the substrate is 5 nm or more.
 10. The memberhaving a photocatalytic function according to claim 2, wherein saidundercoat layer and said photocatalyst layer, are comprised of a metaloxide or a metal oxynitride which is crystalline, and at least one ofthe distances between oxygen atoms in the crystals which constitute theundercoat layer is in the range from 90 to 110% with respect to at leastone of the distances between oxygen atoms in the crystals whichconstitute the photocatalyst layer.
 11. The member having aphotocatalytic function according to claim 2, wherein the main componentof said undercoat layer is a crystalline zirconium compound and the maincomponent of said photocatalyst layer is a titanium compound.
 12. Themember having a photocatalytic function according to claim 11, whereinsaid crystalline zirconium compound includes monoclinic zirconium oxidecrystals.
 13. The member having a photocatalytic function according toclaim 12, wherein the electron diffraction image obtained byperpendicularly irradiating the cross section of the layer includes theelectron diffraction image from the (111) plane or the (−111) plane ofthe monoclinic crystal of zirconium oxide, and the interplanar spacingwith respect to the (111) orientation plane measured by the electrondiffraction image or by a bright-field image of a transmission electronmicroscope (TEM) is 2.6 to 3.0 Å, and the interplanar spacing withrespect to the (−111) orientation plane measured by the same method is3.0 to 3.5 Å.
 14. The member having a photocatalytic function accordingto claim 11, wherein said titanium compound is tetragonal titaniumoxide.
 15. The member having a photocatalytic function according toclaim 14, wherein said titanium compound is anatase type titanium oxide.16. The member having a photocatalytic function according to claim 15,wherein the electron diffraction image obtained by perpendicularlyirradiating the cross section of the layer includes the electrondiffraction pattern from the (101) plane of the crystal of anatase typetitanium oxide, and the interplanar spacing with respect to the (101)orientation plane measured by the electron diffraction image or by abright-field image of a transmission electron microscope (TEM) is 3.3 to3.7 Å.
 17. The member having a photocatalytic function according toclaim 2, wherein a metal element is doped in said photocatalyst layer.18. The member having a photocatalytic function according to claim 17,wherein said metal element is at least one of Sn, Zn and Mo.
 19. Themember having a photocatalytic function according to claim 17, whereinthe addition amount of said metal element is 0.1 mass % or more and 1.0mass % or less.
 20. The member having a photocatalytic functionaccording to claim 17, wherein the addition amount of said metal elementis 0.2 mass % or more and 0.5 mass % or less.
 21. The member having aphotocatalytic function according to claim 17, wherein said metalelement is Fe and the addition amount thereof is 0.001 mass % or moreand 1.0 mass % or less.
 22. The member having a photocatalytic functionaccording to claim 2, wherein said photocatalyst layer is a titanium tincomposite oxide layer or a titanium tin mixed oxide layer.
 23. Themember having a photocatalytic function according to claim 22, whereinthe content of tin in said photocatalyst layer is 3 atomic % or more and50 atomic % or less based on the ratio of the number of tin atoms withrespect to the total number of titanium atoms and tin atoms.
 24. Themember having a photocatalytic function according to claim 2, wherein ahydrophilic thin film is formed on the surface of said photocatalystlayer.
 25. The member having a photocatalytic function according toclaim 24, wherein said hydrophilic thin film is made of at lease oneoxide selected from the group consisting of silicon oxide, zirconiumoxide, germanium oxide and aluminum oxide.
 26. The member having aphotocatalytic function according to claim 25, wherein said hydrophilicthin film is made of silicon oxide.
 27. The member having aphotocatalytic function according to claim 24, wherein said hydrophilicthin film is porous.
 28. The member having a photocatalytic functionaccording to claim 24, wherein the thickness of said hydrophilic thinfilm is 1 nm or more and 30 nm or less.
 29. The member having aphotocatalytic function according to claim 24, wherein the thickness ofsaid hydrophilic thin film is 1 nm or more and 20 nm or less.
 30. Themember having a photocatalytic function according to claim 2, wherein atleast said undercoat layer and said photocatalyst layer are formed by avapor phase method.
 31. The member having a photocatalytic functionaccording to claim 30, wherein said vapor phase method is a sputteringmethod.
 32. A method for manufacturing a photocatalytic membercomprising the steps of: forming a peel preventing layer whose maincomponent is an oxide, an oxynitride or a nitride containing at leastone of silicon and tin on the surface of a substrate; forming amonoclinic zirconium oxide layer at low temperature on said peelpreventing layer; and forming a photocatalyst layer constituted of acrystalline phase on said monoclinic zirconium oxide layer.
 33. Themethod for manufacturing a photocatalytic member according to claim 32,wherein said monoclinic zirconium oxide layer is formed at temperatureof 150° C. or below.
 34. The method for manufacturing a photocatalyticmember according to claim 32, wherein said monoclinic zirconium oxidelayer is formed by a sputtering method.